A method and arrangement for controlling the operation of mobile communication equipment in a power-off state
The invention is related to controlling the operation of mobile communication equipment in a power-off state.
Mobile communication equipment, even in a power-off state, must be capable of reacting to certain excitation signals, and of changing to a power-on state in response to said signals. This is normally realized as follows: even in a power-off state, the power supply unit of mobile communication equipment is partly active, and it monitors certain signals which may provide an impulse that causes a change to a power-on state. Signals typically monitored in a power-off state correspond to battery voltage, charging, pressing of a power switch, and a clock alarm.
In a conventional implementation, the power supply unit of mobile communication equipment comprises control logic and an oscillator for generation of time constants. The type of oscillator used is not important as such in the solution explained herein, but a 2 kHz RC oscillator found in certain devices presently in use, and a 32 kHz crystal oscillator designed for newer devices, may be mentioned as examples. The monitored signals may be analog, direct voltage signals, whose level is monitored and compared to corresponding threshold voltages, or they may be digital signals, whose state is detected. For this, the power supply unit comprises a necessary number of comparators and reference voltages, as well as digital circuits for realizing the necessary state machine.
In solutions of the prior art, the signals are monitored continuously. The current consumption of comparators may be 100-400 xcexcA, for example, and additionally, for example, about 100 xcexcA of current is consumed in keeping the digital circuits on. Therefore, the current consumption of a power supply unit in a power-off state typically may be 300-450 xcexcA, for example.
The purpose of the present invention is to provide a solution that may be used to noticeably decrease current consumption in a power-off state.
A method according to the invention for controlling the operation of mobile communication equipment in a power-off state, in which part of the mobile communication equipment is kept in operation for receiving and analyzing at least one signal, is characterized in that, in said method only a first part of the mobile communication equipment, which essentially consists of timing means, is kept in operation continuously, and a second part, provided for receiving and analyzing said signals, of the mobile communication equipment is controlled by means of said first part to operate and analyze said signals during specified time intervals, and to be inoperative at other times.
In an advantageous embodiment of the method, during each specified time interval the signals are sampled and the samples are analyzed. Furthermore, the signal samples may be multiplexed and analyzed consecutively during said specified time interval.
The specified time intervals may be one tenth or less of the total time, and, for example, of the order of 100 ms in duration.
An arrangement according to the present invention for controlling the operation of mobile communication equipment in a power-off state, in which part of the mobile communication equipment is kept in operation for receiving and analyzing at least one signal, is characterized in that, said part of the mobile communication equipment includes a first part, which essentially consists of timing means and is intended to be in operation continuously, and a second part, which is controlled by means of the first part to operate and analyze said signals at specified time intervals, and to be inoperative at another time.
In an advantageous embodiment, the second part includes means for taking samples of the signals during the specified time intervals, and it may also include means for multiplexing the samples.
In an advantageous embodiment the signals are direct voltage signals and the arrangement includes means for normalizing the signals. In that case, the means for analyzing the samples advantageously include means for comparing, by which each sample may be compared in succession to the same reference voltage.
A noticeable savings in the power consumption of mobile communication equipment in a power-off state is realized by means of the method and arrangement according to the present invention. During the interval between samplings, the current supply is also switched off in the power supply unit, except for the sampling timing circuit, which may be realized using a clock divider, for example. In an advanced implementation, a timing circuit requires 10-50 xcexcA of current. As the interval between samplings grows, the average current consumption of the entire power supply unit in the power-off state approaches this current. At the same time the structure of the power supply unit can be simplified, because after the samples are multiplexed, they can be analyzed using the same means.